A variety of techniques are utilized for angular position sensing. Optical, resistive, electrical, and electrostatic and magnetic fields have all been utilized with sensing devices to measure position. There are many known devices that utilize optical, resistive, electrical, magnetic and other such energies for sensing. Examples of such sensing devices include resistive contacting sensors, inductively coupled ratio detectors, variable reluctance devices, capacitively coupled ratio detectors, optical detectors utilizing the Faraday Effect, photo-activated ratio detectors, radio wave directional comparators, and electrostatic ratio detectors. In addition, there are many other sensors/detectors that are not mentioned herein.
Each of these detection methods offers much value for one or more applications, but none meet all application requirements for all position sensing applications. The limitations may be due to cost, sensitivity to particular energies and fields, resistance to contamination and environment, stability, ruggedness, linearity, precision, or other similar factors. Transportation applications generally, and specifically automotive applications, are very demanding.
In mechanical and/or electromechanical systems, such as for example, automotive applications, motion can be initiated and controlled by rotating a member such as a shaft (e.g., camshaft, crankshaft, and so forth). The angular motion of the shaft is then translated into some other motion, such as linear displacement, rotation of a pump or fan, or the angular rotation of some other intermediate part at a different angular velocity or spatial orientation. Numerous mechanical means such as gears, cams, pulleys, and belts are commonly employed in translating the angular motion of an input shaft to drive an output device. Camshaft and crankshaft mechanisms, for example, are well known in the mechanical transportation arts. Thus, a need exists for sensors that can properly monitor motion and position in such mechanical systems. In engine cam and crank applications, for example, recently manufactured
Cars require precision rotary sensors for high performance and fuel economy. Such engines often utilize electrical-mechanical solenoids to control the engine valves. The opening and closing of such valves are not controlled by a fixed cam but can be controlled by a microprocessor that receive inputs from precision rotary sensors regarding the crank and/or cam speed, torque, load, exhaust gas mixture, oxygen content, and so forth. In this manner, an engine can be achieved that is both efficient and high performing.
One example of a rotary position sensor that can be implemented as sensor 102 is disclosed in U.S. Pat. No. 6,747,448, entitled “Rotary Positions Sensor Methods and Systems,” which issued to Dale Berndt on Jun. 8, 2004 and is incorporated herein by reference. U.S. Pat. No. 6,747,448, is assigned to Honeywell International Inc of Morristown, N.J. Another example of an angular or rotary position sensor is disclosed in U.S. Pat. No. 6,759,843, entitled “Sensing Methods and Systems for Hall and/or MR Sensors,” which issued to Gregory R. Furlong on Jul. 6, 2004 and is incorporated herein by reference. U.S. Pat. No. 6,759,843 is also assigned to Honeywell International Inc. of Morristown, N.J.
Thus, a critical need exists for high performance camshaft and crankshaft position sensors. A major problem with current camshaft and crankshaft sensors that often such devices often do not pass required EMC and radiated emissions and/or conducted emissions testing. The purpose of emission testing is to verify that the product's spurious and unintended emissions do not exceed a level that will interfere with the operation of other electronic/electrical devices. Conducted EMI (i.e., conducted emissions) is usually measured in the shielded enclosure with the device configured such that all cables and peripherals are connected in a manner consistent with normal operation. Conducted EMI is measured as the RF noise voltage injected back into the mains supply by the device. Measurements are made on both the power and ground line in turn, over the frequency range 150 kHz to 30 MHz. The lower frequency extends to 9 kHz for some devices such as lighting. The noise voltage must be below the limit set by the standard.
In order to ensure that such sensors pass required EMC and radiated emissions requirements, it is believed that a new configuration and sensor design should be implemented. Such a design is disclosed herein.